# Re: Another stab at the universal present moment - a gedanken..

```Have you considered that people understand what you mean, but just don't
*agree* with your intuition? I am an eternalist rather than a presentist
(see http://plato.stanford.edu/entries/time/#PreEteGroUniThe or
https://en.wikipedia.org/wiki/Presentism_(philosophy_of_time) and
https://en.wikipedia.org/wiki/Eternalism_(philosophy_of_time) for a
discussion of the two ideas), so I don't think your observers in New York
and San Francisco "share a common present moment" in any objective sense,
and even the ones standing next to each other don't precisely, except in
the limit as their size and distance from each other goes to zero.
Different inertial frames would disagree on the precise picosecond reading
of one person's clock at the "same time" that the other person's clock
shows a particular precise reading (though there is a limit to how much the
frames can disagree, which gets smaller as the distance between the
observers with clocks shrinks), and all these frames are equally valid
(regardless of whether the observers share a common rest frame or not--the
fact that they might share a common frame wouldn't somehow invalidate the
perspective of other frames).```
```
Perhaps the problem is not that we eternalists can't understand presentism,
but that you are actually having some trouble even imagining what
eternalism really means? If so, try this analogy. Say we have some pieces
of rope embedded in a frozen block of ice. Now say we use an MRI machine to
scan a series of 2D cross-sections of the ice and then use each
cross-section as a frame in an animated movie, we may see the
cross-sections of each piece of rope "moving around" relative to one
another, but in the original block of ice this just corresponds to the
ropes' static shapes bending around in different directions--if the axis
perpendicular to the slices is labeled the z-axis, then we can say that the
x and y coordinate of each rope varies as a function of z, but this is just
a description of a shape rather than of movement (change with time).
Further, we would be free to put the block of ice back into the MRI machine
at a different angle so the new series of 2D cross-sections would be skewed
relative to the first series, producing a different animated movie of rope
cross-sections dancing around. But there has been no change in the 3D block
itself or the shape of the ropes embedded in it, this is just a change in
how we view it. That is pretty much how an advocate of eternalism or "block
time" views things--what's real is the 4D spacetime with observers and
other objects as 4D "worms" embedded in it, and there is no single correct
way to slice this 4D spacetime up into a series of 3D cross-sections.

Jesse

On Fri, Dec 27, 2013 at 6:57 PM, Edgar L. Owen <edgaro...@att.net> wrote:

> All,
>
> I haven't made any progress getting the idea of a common universal present
> moment across so here's another approach with a thought experiment....
>
> To start consider two observers standing next to each other. Do they share
> the same common present moment? Yes, of course. Any disagreement?
>
> Now consider those two observers, one in New York, one in San Francisco.
> Do they share the same common present moment? In other words is the one in
> San Fran doing something (doesn't matter what) at the exact same time the
> one in New is doing something? Yes, of course they do share the same
> present moment. Any disagreement?
>
> Now consider an observer on earth and an observer in some far away galaxy.
> But with the condition that they share the exact same relativistic frame in
> the sense that there is zero relative motion and the gravities of their
> planets are exactly the same so that clock time is passing at the exact
> same rate on both their clocks.
>
> Now are these two observers sharing the exact same present moment as well?
> Note that we just extended the exact same relativistic circumstances of the
> previous two examples so there can be no relativistic considerations. Do
> these two observers also share the exact same present moment as well? Yes,
> of course they do. Not only do they share the exact same present moment but
> they also share the exact same clock time t value. Any disagreement?
>
> OK, if you agree then you have to take a partial step towards accepting my
> thesis of a common universal present moment. You now must agree that there
> is at least a common universal present moment across the universe for all
> observers in the same relativistic frame.
>
> Agreed?
>
> Edgar
>
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